erase process has failed click done to continue

From the picture you posted, it looks like the disk you are trying to erase is the same one that contains your operating system. You can't erase your boot disk because the system is using it to run the computer.

You would have to start up from another operating system, either on an external hard drive or possibly your recovery partition. But if you do, you'll need to reinstall Mac OS X before the computer can run normally again.

Is this what you are trying to do?

Try selecting the Macintosh HD and erase that. Depending on the age of your computer, you can also try erasing the disk while booted into Internet Recovery.

Back up your data.  Try booting into Internet Recovery (command - option/alt - R on a restart). It is a slow process. This will install the newest OS that the computer is compatible with. Reformat the drive using Disk Utility/Erase Mac OS Extended (Journaled), then click the Option button and select GUID. Quit Disk Utility. Then install the OS. When the computer restarts, you can use Setup Assistant to restore your data from Time Machine. See the 2nd link for other options.

OS X Recovery

OS X Recovery (2)